This invention relates generally to optical couplers including a photoemitter/detector pair.
Commonly, a photoemitter is aligned with a photodetector in an optical coupler to detect the imposition of an object between the photoemitter/detector pair. For example, a shutter may open or close between the pair and this may be detected by emission from the photoemitter that is detected (or not) by the photodetector.
The photoemitter may be a light emitting diode (LED) which emits light in the visible or infrared spectrum. The photodetector may conventionally be a phototransistor. Commonly, such photoemitter/detector pairs are used in connection with a mouse cursor control device in a computer system. One type of mouse is utilized in connection with wireless systems. In such cases, the wireless mouse may include its own internal battery. Thus, the need for a low power photoemitter/detector pair may be particularly acute in such applications.
Techniques have been developed to decrease the power dissipation of the photoemitter/detector pairs. One such technique is to pulse the LED. Pulsing the LED may reduce power consumption but it also may be adversely affected by the parasitic capacitance of the photodetector.
Another technique for reducing the power consumption of the phototransistor is to increase the value of its load resistor. However, this approach may slow down the response time of the phototransistor.
Thus, there is a continuing need for better ways to reduce the power consumption of photoemitter/detector pairs.
In accordance with one aspect of the present invention, a photodetector circuit may include a pulsed photodetector device. A load is coupled to the photodetector device.
Other aspects are set forth in the accompanying detailed description and claims.